This was my first article on the NEX system, in May 2010. In this I identified all the types of lens which would be adapted to work with the NEX (and later were), and also proposed a 0.66X reducing converter to adapt Alpha lenses to cover the NEX format with increased aperture:

Here's the relevant bit:

"You name it, the NEX will be able to do it. Telescopes, microscopes, endoscopes, whatever. And Alpha lenses, and MD lenses. There is even enough ROOM with over 25mm the spare to fit a true retrofocus format reduction converter – that is, a 0.66X optical unit which condenses the image from a full frame lens to fit the APS-C sensor. It is already done in the video and ciné world, and these converters have a wonderful bonus. Your 24-70mm f/2.8 SSM lens becomes, with a 0.66X reducing converter behind it, a 16-46mm f/2. That’s right – the same way a teleconverter loses you a stop or two, a format reduction converter gains you a stop.

The same converters also increase resolution, much as teleconverters reduce it. Zeiss can achieve 400 line pairs per millimetre from high grade 35mm format movie lenses when rear-converted to reduce on to 16mm or video.

Will Sony ever make such a converter? Do they even know that Zeiss have designs, and make exactly this type of converter for Arriflex and other systems via Angenieux? Do they realise that rear fitting format-reduction converters can also perform an AF function, allowing a manual focus lens from Nikon, Canon, Contax, Minolta or whoever to be mounted on a converter which has an ultrasonic AF mechanism of its own?

Imagine that – your 50mm f/1.2 Rokkor becomes an autofocus 33mm f/1.0 on the NEX. This is not blue sky thinking, it’s an optical practicality not a mere possibility. However, you don’t want to know the price of Zeiss converters, and for a system like NEX a universal converter might never be possible; it might have to be matched to the prime lens."

About making old manual focus focusing, I have in a box somewhere in the house an old Sigma MD to AF converter 1.6x that allow any MD lenses to auto focus, unfortunately the firmware inside the adapter looks to work only on old Minolta 5000 , 7000 and 9000 . I remember having tried it on 800si , 9xi, 7d and Sony A700 and it was not working.

I saw the write-up on that Metabone converter and was suitably impressed. I did remember David's suggestions back in 2010 and must say that I admire him for his foresight. Personnally I have no use for such a device as I only now possess one FF lens, namely Tamron's motorised 70-300 lens. On the other hand I think that InTheSky is on to something when he mentions Canon T&S lens. I remember some discussion about this Samyang T&S about which David was quite positive. http://www.dpreview.com/news/2012/09/07 ... shift-lensI wonder if this lens in Canon mount on a Metabone converter would be just the job on my NEX-6? Could also wait and purchase both items with Sony A mount.Any views on such a set-up?

This does look interesting, but as always I'll wait for some good reviews first. I have the 90, 45 and 24 Canon T&S lenses as well as other full frame lenses. But the thought of retaining something closer to the original full frame focal length has a lot of appeal with wide angle lenses in particular. Pity Metabones don't seem to use distributors, only purchase direct. The dollar prices are quite good when converted into pounds, but of course you run the risk of customs adding VAT and handling charges.

Greg - Minolta did this once. They made a 1.7X teleconverter including AF for MD lenses. It was very rare indeed and only surfaced in Japan. It was called an AF converter for MD/SR type lenses. You can make any optical converter do AF by building in a motor to move the optical element.

Ah so, a moving element group in the adaptor, now it’s making some sense and why it costs so much, although some FF lenses move their rear group quite a distance already so I assume that you would park the lens focus at infinity but I wonder if the distance available to the adaptor would be enough, maybe as it is a field reducer the range of movement would also decrease as an offset and perhaps with a slight gain (due to the smaller format) in field thickness also? T values would change but with the light loss from the extra element group maybe not by a lot? A whole stop is double the amount of light which seems on the face of it rather high expectations, it will be interesting to keep an eye on that one to see what transpires.Greg